Screen vehicle



Patented Nov. 11, 1952 UNITED STATES PATENT OFFICE" SCREEN VEHICLE William 0. Morris, Mayfield Heights, Ohio, as-

signor to The Harshaw Chemical Company,

Cleveland, Ohio, a corporation of Ohio No Drawing. Application October 21, 1950, Serial No. 191,481

This invention relates to an improved method of applying glass enamel or ceramic coatings to glass or metal objects, and to improved compositions for use in such process.

It has long been customary to apply designs to objects to be decorated by the use of a screen having certain portions blocked off to form a design. The screen process has taken numerous specific forms and, for the most part, the enamel constituents have been suspended in a suitable oil known as screen oil. The mixture of screen oil and enamel'constituents is pressed or squeezed through the screen into contact withthe object to be decorated, and is dried thereon. Another form of the screen process involves the use of .a vehicle, in. place of the screen oil, which is solid 'at the temperature of the object to be decorated, ordinarily room temperature, and which is ap plied at a temperature at which it has a suitable consistency. This form of the "screen process has the advantage that itis not necessary to. wait for the object to dry before it is sent to the next operation. It is with this type of screen process that the present invention is concerned.

. I have now discovered certain novel compositions of the-type indicated which are characterized in having highly-desirable properties rendering them suitable for the indicated use. These are useful especially in a process comprising applying such compositions by means of a metal screen of usual type except that it is heated during application of the design by passing electric current therethrough to an extent to keep the surface at a temperature sufiiciently aboveithe melting point of said compositions to prevent clogging. In this way the compositions which are plastic or pasty at the temperature at which they are held just prior to application, neednot be held at as high a temperature as would be I necessary if the screen were not heated.

An optimum specific example is as follows:

Per cent Polyethylene glycol of molecular weight 1,540- 20 Polyethylene glycol of molecular weight 4,000 40 Polyethylene glycol of molecular weight 6,000- 40 The polyethylene glycol of molecular weight 3 Claims. (01. s :-:11)

4,000, or of other molecular weight intermediate between 1,500 and 6,000 may be regarded as the fundamental vehicle while a, material of rela-- tively low molecular weight, for example, 1,540, is used to produce suificient flow for good'application, and obliterationof screen marks in the early portion of the firing cycle. The polyethylene. glycol material of higher. molecular weight is employed for the purpose of rendering the filmrelatively hard at room temperature and to reduce the tendency of the coating .to run on firing. The foregoing compositions can be improved .by the addition of a small percentagei'of ureayalthough its addition is not absolutely essential. Urea. however, is desirably added up to 7 /2% of the combined weight of polyethylene glycols. The urea renders the film somewhat tougherjat the temperatures-at which I prefer to operate without tending to cause the composition to adhere to the heatedscreen. j] The above indicated compositions may be mixed with the enamel constituents (pigment; and flux) in a ratio offrom 20 to 40parts ofthe vehicle to to 60 parts of the enamel constituents;

Another class of compositions may consistiof (1) diphenyl, (2) hydrogenated rosin, and (3).;an ethylene glycol ester of hydrogenated rosin. Such compositions maybe used in proportions, for ex-. a p a o s .9. 1.

- Parts' y weight Diph yl :---'-,40:to:.90 Hydrogenated rosin of melting point 168 F., acid value 162, and density at j; 25 C. 1.045 2=toz20 Ethylene glycol ester of hydrogenated rosin of melting point 131 F., acid value 0 to 15, anddensity at25 C. about 1.06

To the foregoing composition it maybe de sirable to add a diethylene glycol ester ofhydrogenated rosin of lower melting point, for example, one having a melting point of 104? F., acid value 0 to 15, anddensity at 25 C. abouti'1.05. This may be added to'the extent of up to. 30%. It is also desirable, but not necessary, to add a polybutene of molecular weight from' 40,000. to 120,000 to the extent of up to 10% of the weight of the three first named constituents.

In this case, as before, the vehicle may be mixed with the refractory enamel constituents, in the ratio of from 20% to 40% of the vehicle to 80% to 60% of the refractory components.

Diphenyl may be regarded as the fundamental vehicle, and the other materials as additives for modifying the properties of the diphenyl. Ethylene glycol esters, or diethylene glycol esters, of hydrogenated rosin render the freezing point of the mixture somewhat less sharp, and make the coating less brittle. Polybutene acts as a bodying agent and also aids suspension of pigment in the vehicle.

Specific examples of compositions suitable for my purpose are as follows:

Example I Parts by wt. Polyethylene glycol of molecular weight 1,540 20 parts bywt. Polyethylene glycol of molecular weight 4,000 40 parts by wt, Polyethylene glycol of molecular weight 6,000 40 parts bywt. Enamel (pigment and flux) '70 Example II Parts by wt. Composition of Examplel 100 5 Example. III a Parts. bywt. Diphenyli 65 Hydrogenated rosin, melting point 168 F.,

7 acid. value 162, specificv gravity 25 C.

Ethylene glycol ester of hydrogenated rosin, melting point 131 F., acid value 15, specific gravity 25 C. 1.06 25 Example IV Parts by wt.

Compcsiticnof Example III 100 Diethylene glycol ester of hydrogenated rosin,

melting point 104 F., acid value 15, specific gravity 25 C. 1.05

Polybutene molecular weight 40,000 5 Compositionsof the typesindicated maybe applied to glassor metal in the following manner:

The compositionmade'up of the above indicatedvehicle, together with the-enamel constituents inthe proportions indicated, is applied to the glass-or metal surface through ascreen having a suitable design. The temperatureof the composition just before application'will be such asito afford the desired working consistency and preferablywill befrom about '55- C. to 115 C. The screen will be heated by the passage of an electric current therethrough, and will be maintained' at-a temperature ator somewhat above the temperature of the composition to-be applied to the screen, preferabl-y about 5? C. thereabove or about 60 C. to 120 C. The-objects to be decorated will ordinarily be at room temperature (usually 25 C. to 35 C.) although they may be somewhat above or somewhat below room temperature. In any event, the temperature of the object to be decorated will be sufiiciently below the freezing temperature of the composition to be applied that immediately upon application the composition will freeze, thus permitting another application of a different color immediately in the case of multi-color printing, or permitting immediate transfer of the objects to the lehr where the organic material is driven oif'by the calcination leaving the inorganic enamel constituents fused on the objects to be decorated.

Screen enamels of various types may be used. The low melting fluxes of the lead boro-silicate type mixed with suitable coloring oxides and various additions for imparting specific properties to the enamels, such as T102 for acid resistance, are typical. The above described compositions not only have properties suitable for the application, but volatilize on firing without causing defects in the enamel coating.

It will be understood. that the components of the composition are thoroughly admixed before being applied. The mixing is best accomplished by grinding the ingredients togethersuitably in a paint mill of the three-roll type. Desirably the vehicle, the enamel ingredients, and the mill, are all maintained at a temperature'within the range from C. to C. during the mixing,

2. A composition as defined in claim 1 further characterized in that it contains up to 7 5% of urea based on the weight of polyethylene glycols.

3. A: composition suitable for use as a vehicle for enamel to be applied by a screen process, the same essentially consisting of:

Ste 35 Parts by wt. Polyethylene glycol ofmolecular weight about 1,540 Polyethylene glycol of molecular weight ofapproximately 4,000 10 to 70 Polyethylene glycol of molecular weight of approximately 6,000 10 to '70 Urea up to 7 70 of the combined weight of the polyethylene glycols.

WILLIAM C. MORRIS.

REFERENCES CITED The following references are of record in the file of this patent:

Synthetic Organic Chemicals, pub. of "Carbide & Carbon Chemicals Corp, 12th ed., July 1, 1945, pgs. 19-23. 

1. AN ENAMEL COMPOSITION ADAPTED TO BE APPLIED BY A SCREEN PROCESS, THE SAME ESSENTIALLY CONSISTING OF FROM 80 TO 60 PARTS OF ENAMEL CONSTITUENTS AND FROM 20 TO 40 PARTS OF VEHICLE OF THE FOLLOWING COMPOSITION: 